Effect of Nano-CaCO 3 on the Sealing Efficiency of Grouts in Flowing Water Grouting
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pISSN 1226-7988, eISSN 1976-3808 www.springer.com/12205
DOI 10.1007/s12205-020-2373-3
Geotechnical Engineering
Effect of Nano-CaCO3 on the Sealing Efficiency of Grouts in Flowing Water Grouting Yao-Hui Liua,b, Ping Yanga,c, Ze-Bin Ouyanga, Xiao Weib, and Lisha Zhangd Dept. of Geotechnical Engineering, College of Civil Engineering, Tongji University, Shanghai 200092, China Dept. of Civil and Environmental Engineering, National University of Singapore, Singapore 119077, Singapore c Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University, Shanghai 200092,China d Dept. of Civil Engineering, Zhejiang University City College, Hangzhou 310015, China a
b
ARTICLE HISTORY
ABSTRACT
Received 29 December 2019 Accepted 27 May 2020 Published Online 14 August 2020
Flowing water grouting is a big challenge in the tunneling and underground engineering. To enhance the early strength and grouting effectiveness of slurry for flowing water grouting, nano-CaCO3 and fly ash were mixed with cement based grout. A series of physical simulation tests were conducted to simulate the flowing water grouting process in rough rock fracture, and investigate the effect of nano-CaCO3 content on the fluid pressure and sealing efficiency of grouts. Results of viscosity tests show that the viscosity of grouts decreased with an increase of nano-CaCO3 content. Scanning electron microscope (SEM) tests indicate that nano-CaCO3 can promote the formation of fibrous hydrates and enhance the flowing water resistance of grouts. Increasing nano-CaCO3 content resulted in the first increase while later decrease of maximal fluid pressure (MFP) and sealing efficiency (SE) of grouts. Reducing water cement ratio of grouts and incorporating fly ash can effectively improve the SE of flowing water grouting.
KEYWORDS Nano-CaCO3 Flowing water grouting Sealing efficiency Fly ash Viscosity
1. Introduction Grouting is an effective method to prevent groundwater inrush and enhance the rock mass in tunneling engineering (Li et al., 2016; Zhang and Sun, 2019). However, the solidifying rate and early strength of traditional cemented based grouts can’t meet the requirement for flowing water grouting. Therefore, studies on the improvement of characteristics and grouting effectiveness of grouts in flowing conditions draw more attention in recent years. Cement based grouts and chemical grouts are most widely used in flowing water grouting (Zhou et al., 2019; Liu et al., 2020). However, the cost of chemical grouts is high and chemical grouts may pose environmental and health hazards (Zhang et al., 2019). Different from the cement used in construction and building, early strength is especially important for cement applied in flowing water grouting. Flowing water will rinse out low early strength grouts, resulting in the decrease of grouts concentration and the failure of grouting (Yang et al., 2018). Therefore, it’s an urgent need to acquire a kind of environment-friendly grouts
with low cost and high early strength for flowin
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